Validation and factorial structure of a standardized neurological examination assessing neurological soft signs in schizophrenia

Abstract 

Although neurological soft signs (NSS) have been consistently reported in patients with schizophrenia, their clinical relevance, the actual impact of treatment or their evolution during the disease are not well clarified, possibly because of methodological limitations of the available tools. We have developed a new standardized examination integrating the assessment of 23 NSS selected from the literature and the rating of well-validated scales for assessment of extra-pyramidal symptoms. We examined 161 subjects (controls, n=48; patients with schizophrenia, n=95; or recurrent mood disorder, n=18). Half of the patients were neuroleptic-free. Schizophrenic patients had significantly higher total score (14.6±8) than mood disorder patients (12.0±7) and controls (5.0±2). Internal consistency (Cronbach's alpha=0.85) and inter-rater reliability were good. Principal component analysis found five consistent factors (‘motor coordination’, ‘motor integrative function’, ‘sensory integration’, ‘involuntary movements or posture’, ‘quality of lateralization’). This scale thus confirmed a factorial structure in agreement with the conceptual areas of interest explored by NSS and should be a useful tool for assessment of the different dimensions of neurological dysfunction in schizophrenia.

Keywords:  Factorial structure, Integrative function, Mood disorder, Motor coordination, Neuroleptic, Neurological soft signs, Schizophrenia